The full extent of the purging of the Conservative party website was revealed on Thursday when it was confirmed that the party has removed videos from YouTube, including the "behind-the-scenes access" Webcameron series.

As David Cameron's former general election speechwriter condemned the deletion of a decade of speeches from the party's website, it has emerged that every video on the Conservatives' YouTube page that dates from before 2010 has been removed or marked as private.

The WebCameron series was the brainchild of Steve Hilton, the prime minister's former policy guru who filmed and edited most of the early videos but who quit his Downing Street post last year in frustration at the slow pace of reform.

Ian Birrell, a close Hilton ally who served as Cameron's speech writer during the general election, on Friday laments the deletion of the speeches and the videos as a sign of the move away from the modernisation project.

Birrell blames Lynton Crosby, the party's campaign director, who has said the Tories need to remove the "barnacles off the boat". Birrell writes: "Now they have appear to have removed a very big barnacle: a decade of speeches, videos and press releases from their own party website. Insiders claim there is nothing sinister in this, saying it is just an attempt to turn the site into a campaigning tool, filling it with current campaign messages rather than clusters of old speeches. But the use of sophisticated software to ensure search engines do not stumble upon these archives slightly undermines this claim."

Birrell suggests that the deletion of speeches will strengthen the hand of critics who say Cameron has abandoned the modernisation project. "It is a shame to hide speeches grappling with some interesting concepts, especially for a politician on the right. The modernisation project was knocked off course by the financial meltdown, but many of the ideas are more pertinent now than the tired traditional themes of bashing burglars, slashing taxes and sending immigrants home."

The Tories said they had deleted their speech archive from 2000 to May 2010 to make the website a more effective campaign tool. "These changes allow people to quickly and easily access the most important information we provide – how we are clearing up Labour's economic mess, taking the difficult decisions and standing up for hardworking people," a spokesman said on Wednesday.

But the party was so determined to block access to speeches from the early years of Cameron's leadership that a file on the party's website instructed sites such as the Internet Archive and Google, which store copies of webpages for posterity, to remove the deleted pages from their databases. (Those instructions have now been removed from the file, called robots.txt).

Labour has taken similar, though less stringent, action. The party's new website only goes back to September 2010, leaving Ed Miliband's keynote speech at the party conference that year the oldest speech available. But unlike the Conservatives, Labour didn't require internet archivists to remove stored versions, leaving pages dating back to July 2002 in the database.

But the Labour changes means that its website contains speeches since Miliband became leader, unlike the Tory website.

The Webcameron videos were launched by the Tories in 2006 with great fanfare and were billed as a way for the public to see a more natural image of the then leader of the opposition.

"I want to tell you what the Conservative party is doing, what we're up to, give you behind-the-scenes access so you can actually see what policies we're developing, the things that we are doing, and have that direct link ... watch out BBC, ITV, Channel 4, we're the new competition. We're a bit shaky and wobbly, but this is one of the ways we want to communicate with people properly about what the Conservative party stands for," the future prime minister said.

Cameron aide Sam Roake described the videos at the time as "a significant change in the way politics has been done".

"It very much represents the values of David Cameron's Conservative party, of openness and community," he said.

The message of transparency was echoed in one of the speeches now removed from the party's website. George Osborne said in 2007: "We need to harness the internet to help us become more accountable, more transparent and more accessible – and so bridge the gap between government and governed."

On Wednesday, Chris Grayling said that there is "a limit to how much you can put and keep on your website year after year", and a Conservative spokesman claimed that the changes to the website were to "allow people to quickly and easily access the most important information we provide – how we are clearing up Labour's economic mess, taking the difficult decisions and standing up for hardworking people."

When asked about the YouTube deletions and why it was necessary to remove webpages from the Internet Archive, a spokesperson for the Conservatives declined to comment.

"I think it's a bad attempt to airbrush some of their most embarrassing online and offline moments from their past, but obviously the public won't be fooled by it," said a Labour source.

Jim Killock, executive director of the Open Rights Group, pointed out that the material is still available on the UK Web Archive, a project run by the British Library to archive British websites.

Nonetheless, he said: "The suspicion has to be that at the point they are engaged in a huge debate about mass surveillance … they are removing the videos where they criticise Labour for doing the same thing. That's why it's absolutely important that that material remains available."

Despite having been variously removed and hidden from YouTube, the Webcameron episodes are still available on Conservatives.com, on a page only accessible through search.